This invention is generally directed to the effective loading and unloading of cargo from a seaworthy ship. More specifically, the method and apparatus of the present invention provides for the efficient loading and unloading of floatable cargo containers onto submersible platforms of twin-hull ships. The method and apparatus of the present invention is particularly effective for the short-sea trade.
As global commerce has expanded, it has become increasingly necessary to effectively transport goods from one location to a remote location that transverses over water. Containers of goods are transported inland by means of railroads, trucks, inland waterway vessels, etc. The permissible range of operation of land-bound carriers or vessels for inland navigation ends at the coast. At that point, cargo transported by inland waterway vessels and to be carried across the sea must be transferred from a non-seaworthy inland vessel to a seaworthy ship.
It is most inconvenient, time-consuming and costly to transfer goods from inland waterway vessels to seaworthy ships, particularly if the goods contained within the waterway vessels need to be repackaged. In utilizing such known techniques, it is often similarly necessary to again repackage the cargo when the seaworthy ship arrives at the importing port and the optimal inland carrier would be inland vessels.
In the prior art, numerous types of vessels for carrying laden inland waterway vessels across the sea were developed. For example, the prior art provides a LASH (xe2x80x9cLighter Aboard SHipxe2x80x9d) carrier, a BACO (xe2x80x9cBArge/Containerxe2x80x9d) liner, and a BarCat (xe2x80x9cBARge CATamaranxe2x80x9d) ship. Each of these prior art vessels requires application specific machinery.
The prior art LASH carrier and BACO liner are ships primarily designed for the deep-sea trade in which time expended for cargo handling after a typically long voyage is less critical than in the short-sea trade with its frequent layover times after short voyages. Both LASH carriers and BACO liners utilize barges specifically built for the carrier vessel. This greatly enhances costs. The LASH carrier takes these barges aboard one after another by means of a ship-borne crane, while the BACO liner floats the barges in and out one after another through its bowgate. Accordingly, the exchange of incoming versus outgoing barges takes much time that contributes to these deep-sea barge carriers not being economically viable in the short-sea trade. The considerably smaller BarCat also relies on barges built specifically for the carrier ship and has proven uneconomical because of its relatively small size.
The LASH carrier, the BACO liner, the BarCat ship, and other earlier barge carriers employ barges specifically built for the carrier vessel. All of these prior art barges are smaller than inland barges and, because of their small size, are lessxe2x80x94or not at allxe2x80x94economically viable in inland navigation. In fact, the repacking of cargo may be required. Additionally, the exchange of arriving versus departing barges takes too much time to be economically viable in the short-sea trade.
Particularly for the short-sea trade, a semi-submersible or SWATH (xe2x80x9cSmall Water-plane Area Twin Hullxe2x80x9d) ship has garnered particular attention as a special barge carrier that would effectively transport laden inland vessels across the sea. SWATHs are multi-hulled ships. Each hull is narrow in the plane of the water surface, providing a much greater cross section deeper below the surface. Due to this configuration, a SWATH has no cargo holds inside the hull (dry holds) as is characteristic of conventional vessels, but must carry dry cargo on deck, while the lower section of the hull serves as a buoyant body only. The buoyant body contains ballast tanks which, depending on the various load conditions of the SWATH, are filled with more or less water for keeping the vessel at an effective operating draft. Because it can carry its cargo on deck, a SWATH can accommodate full-size inland waterway vessels of all types such as lighters, push barges, self-propelled barges, or any other floatable containers. Of course, in order to benefit from this advantage, as well as from its economy of scale for the short-sea trade, a large SWATH-type barge carrier must be able to rapidly discharge and load floatable containers despite its larger size.
A specific embodiment of a large SWATH proposed as a carrier ship for floatable containers is described in German Patent Application Serial No. DE 42 29 706 A1, which was invented by the same inventor as the present invention. The ship disclosed in the aforementioned German patent application has been referred to as a Trans Sea Lifter (xe2x80x9cTSLxe2x80x9d). While the aforementioned German patent application is hereby incorporated into this patent by this reference, it is different than the TSL ship shown in FIG. 1. The TSL ship 100 of FIG. 1 has submersible platforms capable of receiving numerous bargesxe2x80x94i.e., floatable containersxe2x80x94in a variety of sizes, not only standard barges. However, due to the carrying of different barges, or of a different number of barges, the process of immersing or raising the platforms is more complex and constitutes part of the present invention.
Ship 100 is a SWATH in the form of a catamaran that, between its bow and stern structures, is subdivided by transverse trusses 5 into several cargo spaces, each of which is equipped with a submersible platform 4 between vertical guides. The submersible platform 4 is capable of being flooded and de-watered for loading and discharging floatable containers 12. When ship 100 is on the sea, the submersible platform 4 should sit well above the water. When exchanging floatable containers laden with goods, ship 100 should increase its draft until its submersible platforms 4 become waterborne. After submersible platforms 4 are submerged, the floatable containers 12 arranged on their deck become waterborne and are exchanged with new floatable containers. Newly laden with floatable containers 12, the submersible platforms 4 should resurface out of the water when ship 100 prepares for continuing its voyage.
While the aforementioned German patent application provided a TSL extremely effective for short-sea trade, new means have been provided for effectively controlling the level of the submersible platforms 4 of ship 100 for loading, unloading, and sea travel.
It is therefore a primary object of the present invention to provide a new and improved method and apparatus for loading and unloading cargo from a multi-hull ship.
It is another object of the present invention to provide a new and improved method and apparatus for loading and unloading cargo from a multi-hull ship in a more economical manner.
It is yet a further object of the present invention to provide a new and improved method and apparatus for loading and unloading cargo from a multi-hull ship at a faster speed.
It is another object of the present invention to provide a new and improved method and apparatus for loading and unloading of floatable containers wherein the ship can accommodate cargo-laden floatable containers of various sizes.
It is yet still a further object of the present invention to provide a new and improved method and apparatus for loading and unloading of floatable containers wherein loading and unloading can be performed simultaneously.
It is still another object of the present invention to provide a new and improved method and apparatus for loading and unloading cargo from a multi-hull ship wherein the levels of the receiving floatable platforms of the ship can be readjusted periodically.
Other objects and advantages of the present invention will become apparent from the specification and the drawings.
Briefly stated and in accordance with the preferred embodiments of the present invention, . . .